time_limit_test.cpp

/*
 * @Author: Chacha
 * @Date: 2022-04-03 10:58:29
 * @Last Modified by: Chacha
 * @Last Modified time: 2022-04-03 11:13:36
 */

#include <iostream>
#include <chrono>
#include <thread>
using namespace std;
using namespace chrono;

// O(n)
void function1(long long n)
{
    long long k = 0;
    for (long long i = 0; i < n; i++)
    {
        k++;
    }
}

// O(n^2)
void function2(long long n)
{
    long long k = 0;
    for (long long i = 0; i < n; i++)
    {
        for (long j = 0; j < n; j++)
        {
            k++;
        }
    }
}
// O(n*logn)
void function3(long long n)
{
    long long k = 0;
    for (long long i = 0; i < n; i++)
    {
        for (long long j = 1; j < n; j = j * 2)
        { // 注意这里j=1
            k++;
        }
    }
}
int main()
{
    long long n; // 数据规模

    while (1)
    {
        cout << "输入n：";
        cin >> n;

        milliseconds start_time = duration_cast<milliseconds>(
            system_clock::now().time_since_epoch());

        // function1(n);
        function2(n);
        //        function3(n);

        milliseconds end_time = duration_cast<milliseconds>(
            system_clock::now().time_since_epoch());
        cout << "耗时:" << milliseconds(end_time).count() - milliseconds(start_time).count()
             << " ms" << endl;
    }
}